Answer:
30 cm
Explanation:
The triangle provided is an isosceles triangle.
Isosceles triangles have two sides of equal length.
This means 31 - 3x = 2x + 1.
We can find the value of x using this.
31 - 3x = 2x + 1
31 - 1 = 5x
30 = 5x
x = 6
The perimeter is the sum of all the sides.
(31 - 3x) + (2x + 1) + (10 - x)
Arrange like terms together
(31 + 1 + 10) + (-3x + 2x - x)
42 - 2x = perimeter
Substitute in the value of x
42 - (2 x 6) = 30